Field of the Disclosure
The disclosure relates to the field of hand-maneuverable welding guns for producing a seam weld and particularly to the hand-maneuverable welding gun provided with a fiber laser. Even more particular, the disclosure relates to the hand-maneuverable fiber welding gun configured with a robust, lightweight configuration, improved laser beam delivery system, effective welding debris-evacuating system and weld quality control system.
Prior Art
Welding is commonly employed as an assembly method for joining several metal parts or sheet materials together into an assembly. Conventional welding methods are readily available and include, for example, arc and resistant spot welding. Fairly recently laser welding has been developed and has provided several advantages over more conventional forms of welding. For example, the sharp focusing of the laser beam allows a concentration of energy capable of providing faster welding with less heat being introduced into the surrounding portions of the parts.
Precision automated or manual laser welding can be performed on industrial laser components with a high degree of accuracy, while eliminating the potential hazards of heat damage and thermal stress to complex manufacturing materials. The known laser spot welding and laser seam welding guns include high precision assemblies, pressure-sensitive hermetic assemblies, and other uniquely designed assemblies. Accordingly, the design of a laser welder is not simple and offers a few structural challenges, as discussed below.
One of these challenges includes welding of workpieces having a complicated geometry. For example, body panels of an automobile are transported to a welding station where a clamping system is imposed to hold the body panels while the welding operations are performed. Due to the configuration of some of the parts to be welded, certain clamping and welding apparatus cannot be utilized as space confines may limit the amount of space available for the necessary maneuvering and the proper functioning of the clamping and welding apparatus. To maximize productivity and efficiency, several different configurations of clamping and welding apparatus must be utilized within one welding station depending on the configuration, speed and cost of the clamping and welding apparatus. Such an approach may entail reduced efficiency and high costs.
A need therefore exists for a compact, lightweight, robust hand maneuverable laser welding gun having a configuration substantially eliminating the necessity of having multiple guns.
A further challenge is associated with laser configurations that are typically used for welding: CO2 and Nd:YAG. Both laser configurations operate in the infrared region of the electromagnetic radiation spectrum, invisible to the human eye.
The Nd:YAG operates at a wavelength of about 1.06 microns. This wavelength is absorbed very well by conductive materials, with a typical reflectance of about 20 to 30 percent for most metals. On the other hand, the far infrared (10.6 micron) output wavelength of the CO2 laser has an initial reflectance of about 80 percent to 90 percent for most metals but can easily supply 10,000 watts which is much greater than the highest output power of Nd:YAG lasers.
Both of the above-discussed laser types are characterized by a large physical size. For example, CO2 systems can occupy an average room to achieve the high powers required. Another commonality between these laser types is the low wall plug efficiency, i.e., low energy conversion efficiency from electrical power into optical power.
Another need, therefore, exists for a laser hand maneuverable welding gun with a laser configuration having a compact and efficient structure.
Still another challenge that was presented by known robotically operated fiber laser welders relates to the impact upon the protective window of an optical head by welding debris from the welding zone which are capable of critically damaging the optics housed in the head. To cope with this problem, a pressurized jet of air is introduced into a light guiding channel downstream from the laser head at high velocities and tangentially to the longitudinal axis of the channel. Since the jet is introduced at an angle to the light propagation, it is known as a cross-jet.
The cross jet however is also associated with a few difficulties. First, because of high velocities, the cross jet forms vortexes within the channel. The vortexes in, in turn, create a pressure gradient between the central channel zone and the channel periphery. With a pressure lower in the central zone, the welding debris accumulated along this zone and damage the protective window with a relative ease. Still a further undesirable consequence of the cross-jet is that the pressure gradient negatively affects the beam. Also, the cross jet is accompanied by high noise levels.
A further need, therefore, exists for a laser head protective system that overcomes the above-discussed problems.
Still another challenge stems from the accumulation of welding debris around a welding zone and particularly in a supporting arm of known welding systems having a two-arm clamping structure. The debris accumulation is detrimental to the quality of a weld and further damages the welder's arms.
As a result, another need exists for a laser-based hand-maneuverable welding gun configured with a system for removing welding debris from the welding zone.
A further challenge is presented by the lack of control of the quality of the weld. However the weld quality is one of, if not the most important parameter of a welding process.
Accordingly, a further need exists for a laser hand-maneuverable welding gun configured with a system for automatically adjusting laser output based on the quality of the weld.